Windows support by Ruben Van Boxem.

llvm-svn: 142235
Cr-Mirrored-From: sso://chromium.googlesource.com/_direct/external/github.com/llvm/llvm-project
Cr-Mirrored-Commit: 073458b1ab5489dce6f2ec789889c377b690ccf4
diff --git a/include/strstream b/include/strstream
index 4ff34a5..5eadefd 100644
--- a/include/strstream
+++ b/include/strstream
@@ -131,7 +131,9 @@
 #include <ostream>
 #include <istream>
 
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #pragma GCC system_header
+#endif
 
 _LIBCPP_BEGIN_NAMESPACE_STD